The invention disclosed herein was made in the course of, or under, a contract with the United States Department of Energy.
The present invention relates to the fabrication of various airfoil-shaped elements employed in gas turbines, particularly stationary gas turbines operating at high temperatures.
Gas turbines require various high strength, precisely shaped airfoil structural elements capable of sustained operation at high gas temperatures. In order to withstand the high gas temperatures and resultant thermal strains involved over a period of time, the structures must be cooled by means of embedded cooling tubes through which a suitable coolant, such as water, circulates.
These elements include stationary airfoil-shaped vanes for directing the flow of hot gases, these stationary vanes being known in the art of stationary gas turbines as "nozzles". An additional type of element is an airfoil-shaped blade which is part of and functions to impart motion to a rotating structure as hot gas is directed into the blade by the vane or nozzle. Such turbine blades are known as "buckets" in the stationary gas turbine art.
These structural elements are conventionally fabricated by means of relatively expensive and complex machining operations by which a number of precision parts such as structural spars, coolant tubes, and skin material are fabricated by precision machining, fitted together, welded, and subsequently diffusion bonded by hot isostatic pressing. U.S. Pat. No. 4,137,619 to Beltran et al. and commonly assigned U.S. patent application Ser. No. 106,681, filed Dec. 26, 1979 by Muth et al. entitled "METHOD OF FABRICATING COMPOSITE NOZZLES FOR WATER COOLED GAS TURBINES", now U.S. Pat. No. 4,283,822, describe methods for fabricating composite gas turbine components.
The present invention provides an alternative method for fabricating water cooled composite nozzle and bucket hardware which provides highly suitable hardware without involving extensive machining operations.